Not applicable.
The invention relates to a method for improving the operating reliability in reeling up of a paper web.
A continuous paper web coming from a paper machine or from a finishing apparatus connected thereto in a continuous, i.e. on-line type manner, is reeled in the reel-up into successive machine reels. The machine reels can be seen as a kind of an intermediate storage for the paper web, in which the paper web is stored in the end of a continuous manufacturing process that precedes reeling up. Reeling up is also used in connection with off-line type finishing processes (e.g. calendering, coating) to reel a full-width paper web into machine reels again after the unwinding conducted in the beginning of said process and the treatment/treatments following thereafter. If the web is slit into part webs in connection with these finishing processes, the results of the reeling up are narrower so-called customer rolls that correspond to the width of the part webs.
Because the reeling up is an essential part of the treatment of the paper web/webs at one or several stages of the production and finishing processes of paper, the operation and operating reliability of the reel-up is thus a significant factor in view of the overall function of said processes. The entire reeling up process should be implemented in such a manner that it does not cause disturbances (e.g. stoppages) in the function of the other parts of the process. In addition, the properties and quality (hereinbelow referred to as reeling quality) of the paper web to be reeled up should not be weakened during the reeling up itself or as a result of the same at later stages of the process.
The aim to better control the reeling up process and to attain a better operating reliability and a uniform reeling quality has led up to the development of the mechanical functions of the reeling apparatuses themselves as well as the control methods controlling these functions.
The structure and function of the reel-ups currently in use are described for example in the book by Mikko Jokio: Papermaking Part 3 Finishing, published by Fapet Oy, ISBN 952-5216-10-1, 1999, pp. 143-235.
In the most advanced, so-called second generation reel-ups (see e.g. Papermaking Part 3 Finishing, pp. 160-165), the most important parameters to be adjusted during the actual reeling up sequence, i.e. reel formation, are the web tension of the paper web passed to the reeling, the pressing force, i.e. so-called nip force between a so-called reeling cylinder that guides the web on the roll and the paper reel that is being formed, as well as the torque of the centre-drive of the reeling core of the paper roll. To attain the desired reeling quality for the paper web and desired treatment properties for the reel that is being produced, these parameters are not necessarily kept constant during the reeling up process, but they are adjusted in connection with the same paper grade as a function of the amount of paper accumulated on the reeling core, and for paper grades that differ from each other it is possible to use different parameter values that change in different ways as a function of the amount of paper accumulated on the reeling core.
During the reeling up sequence the increase in the number of adjustable parameters as well as the aim to better optimize said parameters during reeling also increases the requirements for the control methods used for controlling the reeling up. For example, the international publication WO 99/50719 discloses a control method that utilizes neural network computation to produce optimal control variables for a reeling apparatus of paper during the reeling up sequence according to the desired reeling quality at a given time.
In addition to the adjustments made during the actual reeling up sequence, the reeling up apparatus conducts a change sequence after the reel/reels have been finished, in which the finished roll/rolls is/are transferred away from the reel-up and at the same time a new reeling core/new reeling cores are brought therein and the web/webs are threaded on said reeling core/cores and after the cutting of the web/webs the reeling up is continued thereon. This change sequence also involves several mechanical functions and adjustment and control measures of the same, as is described for example in Papermaking Part 3, Finishing, pp. 162-163.
The above-described increase in the mechanical functions of the reel-up and the use of more complex adjustment and control methods also have effects that reduce the overall operating reliability of the reel-up. The simple reason for this is that as the functions of the apparatus and the system are increased, the number of potential points of failure in the system increases as well. This applies especially to measuring sensors and measuring methods necessary in the above-described more complex adjustment and control methods, which are required in larger numbers and for which higher and higher accuracy demands have to be placed at the same time.
The operating reliability of the reel-up can, of course be improved, if all components that are critical in view of the operation, or at least the components that are most liable to faults, such as for example said measuring sensors, are doubled. It is not, however, technically possible to secure all the components by doubling them, and the drawback of the doubled system is the further increasing complexity as well as significantly higher costs.
The purpose of the present invention is to present a method for improving the operating reliability of the reel-up of a paper web by using a model-based, learning fault diagnostics which is substantially separate from the actual control system of the reel-up.
The method according to the invention is characterized by the following features that improve the operating reliability and controllability of the reeling up process, which features can be attained without securing the components of the reel-up physically i.e. by doubling the components, and thus the increasing complexity of the system as well as the thereby increasing costs can be avoided.
The fault diagnostics according to the invention learns in a learning state in the normal operating modes of the reel-up, including the change sequences of the full roll/rolls and the empty reeling core/cores, the normal dependencies between the control, measuring and actuating variables of the reel-up by monitoring the same.
In a diagnostic state the fault diagnostics detects the malfunctions of the components which are critical in view of the function of the reel-up by monitoring aforementioned measuring, control and actuating variables and comparing them to the model formed in the learning state. The malfunctions are detected when they cause, or advantageously already before they cause a substantial weakening or interruption in the function of the reel-up. When the fault diagnostics detect a fault or changes preceding a likely fault, the fault diagnostics warns the user and/or gives an alarm and shifts to a fault tolerance state, if necessary.
In the fault tolerance state the fault diagnostics actively affects the measuring and/or control variables to maintain the function of the reel-up, compensating on the basis of the learned model the malfunction caused by the fault/faults in the actual control system as well as in the function of the reel-up.
The central advantage of the method according to the invention is that the information required by the fault diagnostics can be collected primarily by means of sensors and measurements of the reel-up itself, which are already in use because of the needs of the actual control system. Fault diagnostics, when implemented separately from the actual control system, can also be easily coupled to different types of control systems to be used in connection with the same.
The analysis of the collected information by means of developed, learning and self-controlled algorithms enables the detection of a likely fault already before it causes a substantial weakening or interruption in the function of the reel-up.
The measuring and control values calculated on the basis of the model formed on the process by the learning algorithm can be utilized to supplement and replace the function of said damaged components.
In addition to the learning and diagnostics during the normal reeling up sequence, information on the function of the components is also collected in connection with the change sequence of the full roll/rolls and/or the empty reeling core/cores, which takes place at fixed intervals. The masses of the full roll/rolls and/or the empty reeling core/cores as well as the masses of the members moved during the change sequence are substantially known, wherein the force and frictions required in the transfer of the same can be predicted when the components of the apparatus function normally, and thus, during the transfer movement this information can be used for controlling the condition of the components that conduct and/or control and/or monitor the transfer movement. By comparing the changes in the measuring, control and/or actuating variables during successive transfer movements within a longer period of time it is possible to obtain information on the changes occurring in the components participating in the transfer movement.